It is well documented in the field of exploration and production of fossil fuels that worldwide oil reserves are finite and being rapidly depleted. Oil production in the United States reached a peak circa 1970 and is rapidly declining. Outside the United States, It is presently believed that peak oil production will reach a climax in approximately ten to fifteen years.
However, despite knowledge of the finiteness of the known reserves, demand for oil production and consumption continues to escalate due to increasing demands for energy within and outside the United States. Accordingly, despite short term price fluctuations in the commodity markets, it is expected that the price of oil will continue to escalate as known oil reserves become increasingly scarce. Eventually the price of oil will become too great to provide reasonably priced energy to fuel the global economy, thereby resulting in severe economic contraction of worldwide output of goods and services.
In addition to the increase in oil prices relating to the increasing scarcity of this commodity in view of increasing demand, the majority of known oil reserves are located in countries that are politically unstable. A government or cartel hostile to world economic growth could hold industrialized countries ransom to its oil by refusing to export its oil or charging ludicrously high prices. Sudden instability of oil production or price due to such hostilities is forecast and modeled to cause great economic rifts in our society. It is therefore important that we increase our reliance and resources on sources of energy that are readily available and renewable.
Other concerns regarding the use of fossil fuels are related to environmental factors. For example, the burning of fossil fuels produces carbon dioxide (CO2) and smog producing compounds, such as unburned hydrocarbons and oxides of nitrogen, which are generally released into the atmosphere. It is known that increasing concentrations of CO2 in the atmosphere have resulted in climatic changes, notably global warming. It is further been predicted that global warning may also eventually cause severe rifts in the global society through the loss of arable land needed to feed an ever-increasing global population. Furthermore, global warming is further causing melting of polar ice caps, thereby raising sea levels resulting in further loss of land for increasing populations.
One such source of energy that is readily abundant and renewable is hydrogen. On a weight basis, hydrogen possesses three times more energy than an equivalent weight of gasoline. There are several known methods of producing hydrogen, for example, coal gasification, partial oxidation of oil, steam methane reforming, and biomass gasification, among others. Although these methods have been shown to be efficacious in the generation of hydrogen, a significant disadvantage and limitation in each of these methods is the co-production of carbon dioxide, which as discussed above is a leading cause of global warming.
An alternative process technology that does not have carbon dioxide as a byproduct is the electrolysis of water. High purity hydrogen and oxygen can be produced using a relatively simple electrolysis method. However, a significant disadvantage and limitation of electrolysis is the high electrical power requirements needed to split water into constituent elements of hydrogen and oxygen. Many factors in the electrolysis method contribute to these power requirements.
For example, since water possesses a high dielectric constant, the resistance in the current path between the submersed electrodes is high. In addition, there is a mass transfer resistance at the electrodes due to the abrupt disruption of the electrolyte at the electrode surface from the evolution of gas. This disruption also increases the resistance to the flow of electrical energy.
Furthermore, the active surface area of the electrodes limits the electrolysis process. Accordingly, a need exists to overcome these inherent disadvantages and limitations of electrolysis to split water into its constituent elements of hydrogen and oxygen.
Water vapor discharges have been investigated by scientists for the purpose of understanding the reaction mechanisms of chemical reactions. The intermediates or free radicals that are formed during the reaction, were the main subject of interest in the historic literature. Another interest in the pursuit of water decomposition, was to find a process of generating hydrogen peroxide. These two paths are what motivated the study of this reaction in a plasma.
An early attempt (H. C. Urey and G. I. Levin, Jounal of the American Chemical Society, 3290-3293, Vol. 51, November, 1929), at understanding the reactions in dissociated water by the Wood's tube was the discovery that water vapor under the influence of an electric discharge dissociated water into hydrogen atoms and hydroxyl free radicals. They noted that the product gas consisted of ⅔ the amount in hydrogen for the conditions that were run in the experiments. The paper does not illustrate any process conditions nor the method of analysis of the gas mix. They also detected hydrogen peroxide in the water condensed in the trap. They attributed the excess hydrogen from the intermediate decomposition of the hydrogen peroxide product and not directly from the water vapor. They give support to this assertion by noting that past observations state that hydrogen peroxide is formed first and then further decomposed to simpler species. Experiments were conducted to determine the presence of hydrogen atoms and hydroxyl radicals, which was confirmed by the activity of the gas. They noted the products from the water vapor discharge were more active than if only hydrogen atoms were present. There was no conclusive proof of the existence of these species as cautioned by the Authors. Another group of investigators (R. A. Jones, W. Chan and M. Venugoplan, The Journal of Physical Chemistry, volume 73, number 11 page 3693-3697, November 1969) were motivated to investigate the formation of hydrogen peroxide using a low pressure microwave discharge. They investigated a range of process conditions using water vapor as the reactant and trapping the products of dissociation in a cold trap at very low temperatures. They determined the yield of hydrogen peroxide under varying conditions. P. J. Friel and K. A. Kreiger, Journal of the American Chemical Society, vol. 80, p. 4210-4215, 1958 investigated the recombination of the high voltage discharge products of water vapor. They used various surfaces in order to effect the recombination reactions and determine the final product composition. They principally focused on using the surface of silica gel to study recombination reactions. They discovered that silica gel did not catalyze the recombination of hydrogen atoms. They speculated that a surface was an active intermediate in the subsequent reactions. The recombination reaction was accompanied by a temperature increase and a green luminenscence on the surface of the gel. It was noted that under these conditions the prinicpal products of the reaction was H2 and O2. The reactions were conducted in a moderately high vacuum (<300 millitorr) and extremely low flow rates (<20 millimoles/hour). In addition, reactions of the water vapor discharge products in a liquid air trap were analyzed and studied. Hydrogen peroxide, water and hydrogen and oxygen were formed. The predominant product were water and hydrogen peroxide as well as hydrogen. Most further studies centered about optimizing the formation of hydrogen peroxide or studying the OH free radical.